"She shot a topless scene, but produces aren't sure if they'll use it," a production source tells the new issue of Us Weekly (on stands now). "They filmed it two ways I one, you see Jen's face and boobs in the same shot. In another, the audience might think it's a body double."

Still, the source insists the famously fit star — who plays a dentist who sexually harasses a male employee (CharlieDay) — had no problem doing nudity. "She knows she can't show off her boobs forever, so she's going out with a bang!"

The naked truth won't be revealed until the flick opens July 8, but in the meantime, the movie's posters will titillate too. "She told marketing to push the envelope on this one and not play it safe," a source says, noting that one will feature Aniston with a banana in her mouth. "The studio is playing up her sexuality, and she's all for it!"